1. Field of the Invention
The present invention is related to personal digital assistants (PDAs) and more particularly to a user input interface for a PDA or the like.
2. Background Description
Portable computing devices, such as what is normally referred to as a personal digital assistant (PDA), are increasing in popularity. A typical PDA is a limited function microcomputer provided with a pressure sensitive liquid crystal diode (LCD) display (a touch pad or a touch screen) for input and output (I/O). PDAs are being adapted for wireless Internet communication, e.g., using a modem for e-mail and web browsing. Further, for text input PDAs are known that have a specialized stroke based alphabet interface, e.g., Graffiti(copyright), a selectable on-screen QWERTY keypad, or an expansion pack keyboard.
As these portable devices become smaller and more specialized, text input has become more difficult and less practical. Typical prior art handwriting recognition software may require users to learn special characters or effect a handwriting style in order to enter text. Text input using the Graffiti(copyright) unistroke (i.e., written with a single pen trace) alphabet can be un-natural because it requires users to adhere to strict rules that restrict character shapes; text input using an on-screen QWERTY keypad is somewhat clumsy because only small reductions in size can be made to keyboards before they become awkward to use. An expansion keyboard is impractical for on-the-go input. With either, the tapping on individual characters or the typing is less desirable than being able to handwrite notes or messages. Meanwhile, the demand for PDA information exchange, e-mail and internet access requires entry and retrieval of increasing amounts of data with the handheld device.
Handwriting recognition (HWR) programs capable of dealing with natural (i.e., unrestricted in style) handwritten input are being developed to add to function and usefulness to PDAs and are crucial to the growth of mobile computing in the communications field. Handwriting recognition software, such as Transcriber (formerly known as CalliGrapher) from Microsoft Corp., allows the user to write anywhere on the screen, including on top of any displayed application and system elements. After a time-out period following a pen-lift, the digital ink is removed from the screen and then recognized, the recognition results are then displayed on the screen as ASCII text, and the next sentence or string of words can be handwritten on the screen.
For small screen sized devices such as of PDAs, what are typically referred to as write-anywhere user interfaces, such as used by Transcriber, allow users to write two or three lines at a time at most, with at best two or three words each, which limits entry and prevents continuous uninterrupted longhand entry. Further, these write-anywhere interfaces are problematic because it is difficult to differentiate whether the stylus is acting as a pointer, for clicking on application icons and the like, or an inking instrument for text entry. A common solution involves an un-natural xe2x80x9ctap and holdxe2x80x9d scheme wherein the pen has to be maintained down without dragging it for a certain amount of time in order to get the stylus to act temporarily as a mouse. This can lead to text input errors and the attendant aggravation and input delays caused by such errors.
Another problem with a write-anywhere user interface is that fingers, as the writer is moving his/her hand through the screen, can often interfere with the (pressure-based) pen tracking mechanism. Simultaneous pressure from the stylus and a carelessly positioned pinky finger can cause the device to mislocate the intended stylus entry point, e.g., the device may use the average of the two contact locations. One solution to these problems has been provided by Seni et al., where a special area at the bottom of the screen is used for handwritten input, inputting one word at a time.
Thus, there is a need for handwriting input user interface that allows continuous handwritten input, entering arbitrarily long streams of text on small palm-sized devices without interruption, i.e., without requiring the writer to stop after every character or word, and free from the ambiguities of write-anywhere interfaces.